System and method of generating images from backside of photoactive layer

ABSTRACT

A display system includes a wedge optical element, a photoactive layer, light director, and light modulator. The wedge optical element has a clear substrate. The photoactive layer receives emitted light that generates an image. The light director is disposed between the photoactive layer and the wedge optical element. The light modulator generates emitted light and is optically coupled to the wedge optical element to direct the emitted light to an angled side of the wedge optical element. The angled side of the wedge optical element is configured to reflect the emitted light toward a backside of the photoactive layer to generate an image viewable by a user on a frontside of the photoactive layer. The light director is disposed to receive the emitted light from the angled side of the wedge optical element and direct the emitted light toward propagating substantially normal to the backside of the photoactive layer.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority under the provisions of 35 U.S.C. §119(e) to U.S. Provisional Application No. 61/636,458 filed on Apr. 20, 2012.

TECHNICAL FIELD

This disclosure relates generally to optics, and in particular but not exclusively, relates to image generation.

BACKGROUND INFORMATION

Displaying information is performed by monitors, televisions, and projectors, just to name a few. Large displays can be prohibitively expensive as the cost to manufacture display panels rises exponentially with display area. This exponential rise in cost arises from the increased complexity of large monolithic displays, the decrease in yields associated with large displays (a greater number of components must be defect free for large displays), and increased shipping, delivery, and setup costs. A scheme of tiling smaller display panels to form larger multi-panel displays is also sometimes used to display information, but that scheme is still quite costly and may include distracting seams between tiles. Projectors can generally project large images, but often suffer from poor contrast ratios. In addition, conventional technologies typically have high power consumption per square inch of displayed information, making displaying images on a large-scale quite costly, especially at acceptable contrast ratios. A display system capable of displaying high-contrast images (especially on a large-scale) with better power efficiencies than conventional technologies is desirable.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting and non-exhaustive embodiments of the invention are described with reference to the following figures, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified.

FIG. 1 illustrates an example block diagram configuration of a display system that stimulates a photoactive layer, in accordance with an embodiment of the disclosure.

FIGS. 2A and 2B illustrate two possible examples of light directors that can be used in a display system, in accordance with an embodiment of the disclosure.

FIG. 3 illustrates an example block diagram configuration of a display system that stimulates a photoactive layer and uses a camera module as feedback, in accordance with an embodiment of the disclosure.

FIG. 4 shows an example configuration of a photoactive layer that includes different photoactive materials arranged in a pattern having pixels and sub-pixels, in accordance with an embodiment of the disclosure.

FIG. 5 is a flow chart illustrating a method of generating an image on a photoactive surface, in accordance with an embodiment of the disclosure.

DETAILED DESCRIPTION

Embodiments of a system and method for generating images from a backside of a photoactive layer are described herein. In the following description, numerous specific details are set forth to provide a thorough understanding of the embodiments. One skilled in the relevant art will recognize, however, that the techniques described herein can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring certain aspects.

Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

Throughout this specification, several terms of art are used. These terms are to take on their ordinary meaning in the art from which they come, unless specifically defined herein or the context of their use would clearly suggest otherwise.

FIG. 1 illustrates an example block diagram configuration of a display system 100 that stimulates a photoactive layer 133 to generate an image, in accordance with an embodiment of the disclosure. The illustrated display system 100 includes a light modulator 105, wedge optical element 150, light director 115, and photoactive layer 133. Light modulator 105 emits image-forming light 106 and is optically coupled to wedge optical element 150. Wedge optical element 150 directs image-forming light 106 (via light director 115) to stimulate photoactive layer 133 to form an image displaying image light 199.

In one embodiment, light modulator 105 includes a steerable laser that can be directed to the proper two-dimensional coordinates of the angled side of wedge optical element 150 to form an image on photoactive layer 133. The laser may be capable of raster scanning and may be coupled to a servo motor. In one embodiment, the laser is coupled with an electric lens to selectively focus the laser light onto the angled side of wedge optical element 150. In one embodiment, light modulator 105 includes a laser with micromirrors paired with micro-electro-mechanical systems (“MEMS”) actuators, such as Digital Light Processing (“DLP™”) technology. The laser may be capable of modulating a duty cycle and/or intensity of the laser light output.

Light modulator 105 may include multiple lasers that are configured to emit laser light at different wavelengths where the wavelengths depend on the material in photoactive layer 133. Possible photoactive materials include photoluminescent and photochromic materials. Photoluminescent materials absorb energy from photons from non-visible light and re-emit the energy from the photons as visible light. Photochromic materials are “reflective” in that they reflect visible (e.g. ambient) light and can be stimulated to change how they reflect the visible light, including reflecting specific colors of visible light. The stimulation of the photochromic materials may be done by visible light, and/or non-visible light (e.g. ultraviolet (“UV”), near-infrared (“NIR”), infrared (“IR”)). In one example, a chemical composition known as Spiropyrans are stimulated with UV light, which causes a chemical reaction that makes the Spiropyran chemical reflect colored light. Another possible photoactive material would be a thermochromic material that changes the light the material absorbs/reflects based on its temperature. Photo-active materials or paints are available from companies such as DuPont™, 3M™, and others. Therefore, using photoluminescent, photochromic, and thermochromic materials separately or in combination offers a wide variety of ways to create an image and even color images on a photoactive surface. Light modulator 105 can be configured to include one or more of the appropriate light sources (e.g. lasers with different wavelengths) to stimulate an image on the photoactive material selected.

The “decay time” of the material is the amount of time that the stimulation of the material affects the optical output or reflection of the material. Some of the decay times of the materials can be characterized as “half-lives” because of their rate of decay. As an example, the materials may have half-lives of 0.5 seconds, one second, or thirty minutes. When a material is first stimulated, it may turn black, but then fade to gray, and eventually white if it is not re-stimulated to turn black. The half-lives can vary depending on the particular chemical composition of the material. Some of the materials have more digital or bi-stable characteristics, meaning they don't slowly fade from black to white. Rather, these bi-stable materials may maintain a pigment or color until affirmatively switched back by a stimulus (e.g. certain temperature or wavelength). For these materials, a first stimulation (e.g. light of a first wavelength) may stimulate the material to turn black or “ON”, while a second, different stimulation (e.g. light of a different wavelength than the first wavelength), may cause the material to turn white or “OFF.” For thermochromic materials, the material may be stimulated to a first color by stimulating the material with a first wavelength, which causes the material to reach a certain temperature that causes a chemical reaction. The thermochromic material may then need to be cooled by a different stimulus to cause the material to switch back to white. This may appear as erasing the image by a person that is viewing the thermochromic material.

In one example, a photochromic compound is stimulated with a laser light of a first intensity to cause colorization of the photochromic compound and laser light of a second intensity stimulates the photochromic compound to cause de-colorization of the photochromic compound. In still another example, a photochromic material may reflect different colors of light based on the wavelength of the stimuli. Hence, the same material can reflect red, green, and blue light if stimulated with the proper wavelength of light. Therefore, light modulator 105 may be configured with three or more steerable or guided lasers that can stimulate a material with different wavelengths of light to generate different colors for generating an image.

Due to the decay time of the photoactive material(s), the images displayed by display system 100 on photoactive layer 133 may not have the high refresh rate (e.g. 60 or 120 Hertz) required for watching sporting events or movies and may be best suited for displaying static or slow changing images. However, the decay time may give display system 100 a significant power advantage over conventional displays and projectors. In one example, photoactive layer 133 only needs to be re-stimulated or refreshed every ten seconds, while still maintaining an acceptable contrast ratio. Of course, different photoactive materials may have higher or lower half-lives. The watts per square inch needed to present an image using image generating system 100 may be orders of magnitude less than conventional displays and projectors due to the lower refresh rate required to maintain the image.

Referring to the illustrated embodiment in FIG. 1, light modulator 105 is optically coupled to wedge optical element 150 in a side-emitter configuration and directs image-forming light 106 toward an angled side of the wedge optical element. Wedge optical element 150 is made from a clear substrate and may be glass or plastic. The angled side of the wedge optical element reflects image-forming light 106 in the direction of light director 115 and image-forming light 106 propagates in the wedge optical element until the angle the image-forming light 106 strikes an interface between wedge optical element 150 and light director 115 is greater than the critical angle of Total Internal Reflection (“TIR”).

Ideally, each ray of image-forming light 106 would propagate normal to the backside surface of photoactive layer 133 to form a crisp image. However, if enough of image-forming light 106 propagates at angles that are substantially offset from normal to the targeted areas or pixel area of photoactive layer 133, the wrong pixel area of photoactive layer 133 may be stimulated; neighboring pixels may receive the stimulation intended because of the refracting angle. This unwanted effect may be called “directional bleed” or “spread” and negatively impact the image clarity of the desired image. To mitigate this problem, light director 115 may assist in increasing the amount of image-forming light 106 that strikes the backside of photoactive layer 133 at an angle that is substantially normal.

FIGS. 2A and 2B illustrate two possible examples of light director 115, in accordance with an embodiment of the disclosure. FIG. 2A shows a light directing turning film 215A. Turning films are commercially available and generally include optical structure (on the microscopic level) to bend light. In one example, light directing turning film 215A doubles the bend of light to encourage the light to propagate substantially normal to the backside of photoactive layer 133. FIG. 2B shows light directing glass bead 215B, which may be incorporated in a film. Films that include glass beads may be available from 3M™. The shape of glass beads 215B optically couple image-forming light 106 to photoactive layer 133 in an optically efficient manner. The materials that glass beads 215B are made from may be tuned to couple the particular wavelength or wavelengths of light emitted by light modulator 105. In one embodiment, glass beads are impregnated in the clear substrate of wedge optical element 150.

FIG. 3 illustrates an example block diagram configuration of display system 300 that stimulates photoactive layer 133 and uses a camera module 310 as feedback, in accordance with an embodiment of the disclosure. The illustrated display system 300 includes light modulator 105, wedge optical element 150, light director 115, photoactive layer 133, logic engine 315, and camera module 310 as an environment input 330. Display system 300 may also include environment inputs 330 which may include microphone 332 and proximity sensor 334, as illustrated.

Camera module 310 is positioned to monitor photoactive layer 133 and provides logic engine 315 feedback via image data sent to logic engine 315 through communication link 350. Communication link 350 can be wireless or wired and may also be connected to network 375. Logic engine 315 may analyze the image data and send a command to light modulator 105, in response to analyzing the image data. Logic engine 150 may analyze the image data from camera module 310 for the contrast of the image displayed on photoactive layer 133 and cause light modulator 105 to increase or decrease the refresh rate of the image in response to the image data.

Logic engine 315 may recognize a person (image recognition) using image data from camera module 310 and display images on the wall according to settings configured by the recognized person. Sports scores, stock tickers, weather reports, reminders, calendars, clocks, books, and recipes are possible images for display. Using the image data, logic engine 150 may recognize certain events (e.g. movement in the room) or contexts (ambient light brightness) and cause light modulator 105 to display information in response.

Still referring to FIG. 3, logic engine 315 is coupled to microphone 332 to receive sound signals received by microphone 332. Display system 300 (using logic engine 315) may recognize sounds using microphone 332 and display an image in response. It may respond to voice commands from a user. Display system 300 may recognize songs, televisions shows, or movies and display an image or series of images that correspond with the sound input received from microphone 332. Proximity sensor 334 is configured to receive proximity signals from a tag and communicatively coupled to send a proximity alert signal to logic engine 315 when a “tag” is proximate to the proximity sensor. For example, proximity sensor 334 may receive proximity signals from a “tag” located, for example, on a key chain or embedded in a mobile device, and display system 300 may display an image in response to receiving the proximity signals. It is appreciated that environment inputs 330 may include more inputs and hardware than what is shown in FIG. 3. Environment inputs 330 may include instruments to measure temperature data, humidity data, and/or atmospheric pressure. Logic engine 315 may include a processor a Field Programmable Gate Array (“FPGA”), or other logic for processing image data and environment inputs 330. Logic engine 315 may include memory to store settings, images, and image data received from camera module 310.

A user may be able to communicate with display system 300 (via network 375) with a mobile device or personal computer. A user may be able to change the images or theme of the images displayed by display system 300. Display system 300 may include a BlueTooth or other wireless interface (not shown) for mobile device interface.

It is appreciated that display system 100 could be built into a wall or sold as a panel display. Display system 300 could also be built into a wall or sold as a panel display with camera module 310 being positioned separately to monitor the image displayed on photoactive layer 133.

FIG. 4 shows an example configuration of a photoactive layer 133 that includes different photoactive materials arranged in a pattern having pixels and sub-pixels, in accordance with an embodiment of the disclosure. FIG. 4 shows a view from the frontside of photoactive layer 133. In the upper left corner, FIG. 4 shows a zoomed in view of a pixel of photoactive layer 133 having a first color sub-pixel 406, a second color sub-pixel 411, and a third color sub-pixel 416. Different photoactive materials that emit or reflect different colors of light (e.g. red, green, and blue) are disposed, separately, in the sub-pixels. The light modulator 105 will stimulate the sub-pixels on an individual basis to generate a perceived color of each pixel to form an image. The intensity or duration of stimulation of first color sub-pixel 406, second color sub-pixel 411, and third color sub-pixel 416 may be varied to get the desired color from the pixel. The intensity of the stimulation may be varied by changing a duty cycle of the emitted laser light.

When the first color sub pixels 406 are stimulated, they subsequently emit or reflect a first color (e.g. red) light for a period of time, when the second color sub pixels 411 are stimulated, they subsequently emit or reflect the second color (e.g. green) light for a period of time, and when the third color sub pixels 416 are stimulated, they subsequently emit or reflect the third color (e.g. blue) light for a period of time. By aligning or timing image-forming light 106 from light modulator 105 with the different sub-pixels, the appearance of color images and videos may be created. Of course, other color combinations may be used. By arranging three different colors of photoactive paint on photoactive layer 133, a color display may be created in conjunction with light modulator 105 having a laser of a single wavelength to stimulate the three different colors of photoactive paint to generate a color image.

FIG. 5 is a flow chart illustrating a process 500 of generating an image on a photoactive surface, in accordance with an embodiment of the disclosure. The order in which some or all of the process blocks appear in process 500 should not be deemed limiting. Rather, one of ordinary skill in the art having the benefit of the present disclosure will understand that some of the process blocks may be executed in a variety of orders not illustrated, or even in parallel.

In process block 505, image-forming light (e.g. image-forming light 106) is directed to a backside of a photoactive layer to generate an image on a frontside of the photoactive layer (e.g. photoactive layer 133). In one example, directing the image-forming light to the backside of the photoactive layer 133 may include directing image-forming light to an angled side of a wedge optical element having a clear substrate. In that example, a light director layer receives the image-forming light from the angled side of the wedge optical element and couples the image-forming light to the backside of the photoactive layer in an optically efficient manner. In process block 510, a camera module monitors the image from a frontside of the photoactive layer. The image data is analyzed in process block 515. In process block 520, the image on the frontside of the photoactive layer 133 is completed or refreshed by directing additional image-forming light to the backside of the photoactive layer. The completing or refreshing of the image is in response to the analyzed image data. In one embodiment, the refresh rate of the image is based on a contrast ratio of the image. After process block 520, the process may return to process block 510.

The processes explained above are described in terms of computer software and hardware. The techniques described may constitute machine-executable instructions embodied within a tangible or non-transitory machine (e.g., computer) readable storage medium, that when executed by a machine will cause the machine to perform the operations described. Additionally, the processes may be embodied within hardware, such as an application specific integrated circuit (“ASIC”) or otherwise.

A tangible non-transitory machine-readable storage medium includes any mechanism that provides (i.e., stores) information in a form accessible by a machine (e.g., a computer, network device, personal digital assistant, manufacturing tool, any device with a set of one or more processors, etc.). For example, a machine-readable storage medium includes recordable/non-recordable media (e.g., read only memory (ROM), random access memory (RAM), magnetic disk storage media, optical storage media, flash memory devices, etc.).

The above description of illustrated embodiments of the invention, including what is described in the Abstract, is not intended to be exhaustive or to limit the invention to the precise forms disclosed. While specific embodiments of, and examples for, the invention are described herein for illustrative purposes, various modifications are possible within the scope of the invention, as those skilled in the relevant art will recognize.

These modifications can be made to the invention in light of the above detailed description. The terms used in the following claims should not be construed to limit the invention to the specific embodiments disclosed in the specification. Rather, the scope of the invention is to be determined entirely by the following claims, which are to be construed in accordance with established doctrines of claim interpretation. 

1. A display system comprising: a wedge optical element having a clear substrate; a photoactive layer to receive emitted light that generates an image, wherein the photoactive layer includes a photochromic compound that absorbs the emitted light and, responsive to the absorbed emitted light, generates the image through selective reflection of a wavelength of ambient light; a light director disposed between the photoactive layer and the wedge optical element; a light modulator that generates the emitted light and is optically coupled to the wedge optical element to direct the emitted light to an angled side of the wedge optical element, the angled side of the wedge optical element configured to reflect the emitted light toward a backside of the photoactive layer to generate the image viewable by a user on a frontside of the photoactive layer, wherein the light director is disposed to receive the emitted light from the angled side of the wedge optical element and direct the emitted light toward propagating substantially normal to the backside of the photoactive layer; a camera module positioned to monitor the photoactive layer to generate image data; and a logic engine coupled to receive the image data from the camera module, wherein the logic engine is coupled to send commands to the light modulator to direct and modulate the emitted light, in response to the image data.
 2. (canceled)
 3. The display system of claim 1 further comprising a proximity sensor configured to receive proximity signals from a tag and communicatively coupled to send a proximity alert to the logic engine when a tag is proximate to the proximity sensor.
 4. The display system of claim 1 further comprising a microphone coupled to the logic engine to receive sound signals.
 5. The display system of claim 1, wherein the light director includes glass beads.
 6. The display system of claim 5, wherein the glass beads are impregnated in the clear substrate of the wedge optical element.
 7. The display system of claim 1, wherein the light director includes a turning film.
 8. The display system of claim 1, wherein the light modulator is optically coupled to the wedge optical element as an edge-emitter.
 9. The display system of claim 1, wherein the light modulator includes at least one steerable laser for generating the emitted light.
 10. The display system of claim 9, wherein the light modulator includes a plurality of steerable lasers, wherein the plurality of lasers includes lasers emitting different wavelengths of light.
 11. The display system of claim 1, wherein the light modulator includes a Digital Light Processing (“DLP”) projector for generating the emitted light.
 12. The display system of claim 1, wherein the photoactive layer includes a substantially homogenous mixture of different photoactive materials, the different photoactive materials chemically configured to display different colors of light based on different stimulation from the light modulator.
 13. The display system of claim 1, wherein the photoactive layer includes three or more different photoactive materials arranged to be stimulated by the light modulator as pixels of a color display.
 14. A system for generating an image on a photoactive surface, the system comprising: photoactive layer means for responding to image-forming light incident on a backside of the photoactive layer means by generating the image on a frontside of the photoactive layer means, wherein the photoactive layer means includes a photochromic compound that absorbs the image-forming light and, responsive to the absorbed image-forming light, generates at least part of the image through selective reflection of a wavelength of ambient light; stimulating means for directing the image-forming light to the backside of the photoactive layer means; and light directing means for turning the image-forming light to increase an amount of the image-forming light propagating normal to the backside of the photoactive layer means, wherein the stimulating means is disposed between the photoactive layer means and the light directing means.
 15. The system of claim 14 further comprising: imaging means for generating image data of the image on the frontside of the photoactive layer means; and processing means for receiving the image data from the imaging means and sending commands to the stimulating means, in response to the image data.
 16. The system of claim 14, wherein the stimulating means includes a laser.
 17. A method of generating an image, the method comprising: directing image-forming light to a backside of a photoactive layer to generate the image on a frontside of the photoactive layer; generating image data from a camera module monitoring the image from a frontside of the photoactive layer, wherein the photoactive layer includes a photochromic compound that absorbs the image-forming light and, responsive to the absorbed image-forming light, generates the image through selective reflection of a wavelength of ambient light; analyzing the image data; and completing or refreshing the image on the frontside of the photoactive layer by directing additional image-forming light to the backside of the photoactive layer, the completing or refreshing the image on the frontside of the photoactive layer in response to the analyzed image data.
 18. The method of claim 17, wherein directing the image-forming light to the backside of the photoactive layer includes: directing the image-forming light to an angled side of a wedge optical element having a clear substrate; and receiving the image-forming light from the angled side of the wedge optical element with a light director layer that couples the image-forming light to the backside of a photoactive layer in an optically efficient manner.
 19. The method of claim 17 further comprising adjusting a refresh rate of the image based on a contrast ratio of the image, wherein analyzing the image data includes analyzing a contrast ratio of the image.
 20. The method of claim 17, wherein the photoactive layer includes photochromic material.
 21. The method of claim 17, wherein the photoactive layer further includes photoluminescent material.
 22. The method of claim 17, further comprising: obtaining an image of a person in proximity to the frontside of the photoactive layer with the camera; recognizing the person with a logic engine based on image data; and generating a second image according to settings associated with the recognized person. 